Shell-model picture of virtual detour transitions in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ radiative electron-capture decay

For the first forbidden unique (1u) radiative electron-capture β decay of ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$, a contribution of the γ/β detour transitions via virtual nuclear states to the bremsstrahlung spectrum has been considered in terms of the shell model. Calculations of the matrix elements for the virtual E1 γ and allowed Gamow-Teller β transitions have been performed with the use of the Warburton, Becker, Millener, and Brown interactions. For the effective charge, which describes the contribution of the detour transitions, an interval 0.96<${\mathit{e}}_{\mathrm{eff}}$<1 has been found. The model predictions are fairly close to the experimental value ${\mathit{e}}_{\mathrm{eff}}$=0.78. A possible origin of the small remaining deviation is discussed. © 1996 The American Physical Society.